The present invention relates to a fin stabilized projectile, particularly a kinetic energy projectile having a great longitudinal extent, in which measures are taken to increase the thermal resistivity of the guide fins.
In fin stabilized projectiles fired over great distances at high velocities of, for example, 1500 m/s, friction with the air acting particularly on the leading edges of the fins creates high thermal stresses. Particularly in guide fins made of an aluminum alloy, this may cause the leading and outer edges of these guide fins to begin to melt away in an uncontrollable manner.
Federal Republic of Germany published patent application No. 1,145,963 discloses, as a measure of thermal protection against air friction and overheating of guide fins made of aluminum, to provide such guide fins with a coating of a melamine or a polyamide lacquer or a similar lacquer.
Moreover, U.S. Pat. No. 4,098,194 discloses a fin stabilized high velocity projectile in which aluminum components such as, for example, the guide fins or the ballistic hood, are provided with a hard coating protective layer in order to increase their thermal resistivity. This protective layer is to be applied by the electrolytic deposition of an alkali metal silicate from an aqueous solution.
However, in projectiles whose guide fins are covered by a thin thermal protection layer, it may happen nevertheless that the liquidus temperature of the metal alloy of the guide fins is exceeded in some regions in which case, although the thermal protection layer may remain intact at the front end, the hydrodynamic pressure of the liquid metal may cause the protective layer to break open at the rear and permit the liquid metal to flow out. Tests have shown the breaking-up effect of the protection layer.
Although steel guide machanisms employing solid steel fins have the necessary thermal resistivity, their great weight in the projectile results a high percentage of dead weight which is ineffective in the target.